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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

Modern car paint and rust



 
 
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  #1  
Old February 12th 17, 06:43 PM posted to rec.crafts.metalworking
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Posts: 128
Default Modern car paint and rust

Hi folks,

Quick question. Many cars from the 1980s used to rust badly. Sometime in the 1990s, this changed - and quite suddenly. Does anyone know what specific changes were made to the paint composition and surface treatment? I can only find vague allusions in most articles.

Thanks,

Chris

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  #2  
Old February 12th 17, 07:02 PM posted to rec.crafts.metalworking
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Posts: 1
Default Modern car paint and rust

On 2017-02-12, Christopher Tidy wrote:
Hi folks,

Quick question. Many cars from the 1980s used to rust
badly. Sometime in the 1990s, this changed - and quite
suddenly. Does anyone know what specific changes were made to the
paint composition and surface treatment? I can only find vague
allusions in most articles.


I thought that at some point, they started requiring galvanized body
panels.

i
  #3  
Old February 12th 17, 07:16 PM posted to rec.crafts.metalworking
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Posts: 128
Default Modern car paint and rust

Am Sonntag, 12. Februar 2017 20:02:27 UTC+1 schrieb Ignoramus20243:

I thought that at some point, they started requiring galvanized body
panels.


This is also true, I think. But I don't see the modern paint cracking and falling off, so I'm wondering what's better about the paint.
  #4  
Old February 12th 17, 07:28 PM posted to rec.crafts.metalworking
dpb
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Posts: 12,408
Default Modern car paint and rust

On 02/12/2017 1:16 PM, Christopher Tidy wrote:
Am Sonntag, 12. Februar 2017 20:02:27 UTC+1 schrieb Ignoramus20243:

I thought that at some point, they started requiring galvanized body
panels.


This is also true, I think. But I don't see the modern paint cracking
and falling off, so I'm wondering what's better about the paint.



Don't think there's any "requirement" other than what the manufacturer
thinks suits their purpose best as far as whether panels are/aren't
galvanized (or otherwise treated). I don't know what actually is most
common other than there's a tremendous fraction not that isn't even
metal; just pretty sure there's no mandate same. The mandates are
those for the fuel mileage averages so that means "lighter is better" in
ounces quantities.

As for paint, what has improved is they've finally figured out formulas
that have at least some longevity after the EPA restrictions on VOC's
killed all the traditional finishes as not being within those limits.

--

  #5  
Old February 12th 17, 08:01 PM posted to rec.crafts.metalworking
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Posts: 17,344
Default Modern car paint and rust

On Sun, 12 Feb 2017 10:43:40 -0800 (PST), Christopher Tidy
wrote:

Hi folks,

Quick question. Many cars from the 1980s used to rust badly. Sometime in the 1990s, this changed - and quite suddenly. Does anyone know what specific changes were made to the paint composition and surface treatment? I can only find vague allusions in most articles.

Thanks,

Chris

Big thing was change to the surface preparation of the steel to
either electrostatic wet application or full body dip of a high
quality etching primer which I believe contains Zinc.
This was combined with the use of high strength steels and
"galvanized" steel in rust prone areas.
  #6  
Old February 12th 17, 10:03 PM posted to rec.crafts.metalworking
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Posts: 282
Default Modern car paint and rust

On Sunday, February 12, 2017 at 3:01:15 PM UTC-5, Clare wrote:
On Sun, 12 Feb 2017 10:43:40 -0800 (PST), Christopher Tidy
wrote:

Hi folks,

Quick question. Many cars from the 1980s used to rust badly. Sometime in the 1990s, this changed - and quite suddenly. Does anyone know what specific changes were made to the paint composition and surface treatment? I can only find vague allusions in most articles.

Thanks,

Chris

Big thing was change to the surface preparation of the steel to
either electrostatic wet application or full body dip of a high
quality etching primer which I believe contains Zinc.
This was combined with the use of high strength steels and
"galvanized" steel in rust prone areas.


Right. It's better coatings, better primers and protection, and better application. Read, water-based coatings that often are based on urethanes; phosphate and weldable, etching primers; galvanizing in rust-prone areas; and electrophoresis and electrostatic application. The first water-based coatings -- used into the '80s by some manufacturers -- had poor adhesion and didn't weather well. They're MUCH better now.

All of this became more necessary as body panels got thinner, with the use of AHSS (advanced high-strength steels; a continuing evolution of the HSLA [high-strength, low-alloy] steels that were first used in the '70s). Rust is potentially a bigger problem than ever because the steel is thinner.

--
Ed Huntress
  #7  
Old February 14th 17, 12:54 AM posted to rec.crafts.metalworking
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Posts: 128
Default Modern car paint and rust

Am Sonntag, 12. Februar 2017 23:03:10 UTC+1 schrieb :

Right. It's better coatings, better primers and protection, and better application. Read, water-based coatings that often are based on urethanes; phosphate and weldable, etching primers; galvanizing in rust-prone areas; and electrophoresis and electrostatic application. The first water-based coatings -- used into the '80s by some manufacturers -- had poor adhesion and didn't weather well. They're MUCH better now.

All of this became more necessary as body panels got thinner, with the use of AHSS (advanced high-strength steels; a continuing evolution of the HSLA [high-strength, low-alloy] steels that were first used in the '70s). Rust is potentially a bigger problem than ever because the steel is thinner.


Are these modern coatings two-pack paints? Or some kind of stove enamel which is baked on? I also remember hearing something about paints which contained cyanide at some point.

I'd be interested to know the composition, because they seem way better than anything I can buy.

Thanks for the replies!

Chris
  #8  
Old February 14th 17, 02:43 AM posted to rec.crafts.metalworking
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Posts: 282
Default Modern car paint and rust

On Monday, February 13, 2017 at 7:54:33 PM UTC-5, Christopher Tidy wrote:
Am Sonntag, 12. Februar 2017 23:03:10 UTC+1 schrieb :

Right. It's better coatings, better primers and protection, and better application. Read, water-based coatings that often are based on urethanes; phosphate and weldable, etching primers; galvanizing in rust-prone areas; and electrophoresis and electrostatic application. The first water-based coatings -- used into the '80s by some manufacturers -- had poor adhesion and didn't weather well. They're MUCH better now.

All of this became more necessary as body panels got thinner, with the use of AHSS (advanced high-strength steels; a continuing evolution of the HSLA [high-strength, low-alloy] steels that were first used in the '70s). Rust is potentially a bigger problem than ever because the steel is thinner.


Are these modern coatings two-pack paints? Or some kind of stove enamel which is baked on? I also remember hearing something about paints which contained cyanide at some point.

I'd be interested to know the composition, because they seem way better than anything I can buy.

Thanks for the replies!

Chris


I wish I could give you a simple answer, but the chemistry of automobile paints has exploded in many directions over the past ten years or so, and the chemistry is mostly over my head.

Around the world, each manufacturer seems to use something different. There are water-born systems and solvent-born systems; two-wet and three-wet systems; integrated primers and self-sealing clear coats (Nissan). It's wild out there.

Some of the primers and clear coats are catalyzed before application. I *think* the base coats are not. Some are described as melamine-based; others are described as acrylic, urethane, or polyester. Water-based systems seem to make up the majority. Again, the chemistry is beyond me.

Before I retired I was working on an in-depth study of Ford's production, but I didn't get very far. They have a new two-wet system with no clear coat ("monocoat") and it may be the leading edge. I suspect it's from Axalta.

If you want to talk to someone who specializes in this stuff, I may be able to get you some names.

--
Ed Huntress

  #9  
Old February 14th 17, 01:52 PM posted to rec.crafts.metalworking
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Posts: 8,263
Default Modern car paint and rust

On Mon, 13 Feb 2017 16:54:28 -0800 (PST), Christopher Tidy
wrote:

Am Sonntag, 12. Februar 2017 23:03:10 UTC+1 schrieb :

Right. It's better coatings, better primers and protection, and better application. Read, water-based coatings that often are based on urethanes; phosphate and weldable, etching primers; galvanizing in rust-prone areas; and electrophoresis and electrostatic application. The first water-based coatings -- used into the '80s by some manufacturers -- had poor adhesion and didn't weather well. They're MUCH better now.

All of this became more necessary as body panels got thinner, with the use of AHSS (advanced high-strength steels; a continuing evolution of the HSLA [high-strength, low-alloy] steels that were first used in the '70s). Rust is potentially a bigger problem than ever because the steel is thinner.


Are these modern coatings two-pack paints? Or some kind of stove enamel which is baked on? I also remember hearing something about paints which contained cyanide at some point.

I'd be interested to know the composition, because they seem way better than anything I can buy.

Thanks for the replies!


At some point in the last 2-3 decades, I recall seeing a commercial on
TV where the US mfgr touted that both vehicle frames and body panels
being dipped in a rust-proofing hot bath of some sort. I quit TV 13
years ago, so it was well before that.

The painter at work sprayed my old '72 Int'l Scout with Imron, a
2-part aviation paint. It was over $100/gal way back then ('82,
$3-500 now), but a friend had given it to me, the spare from painting
his '48 Willys wagon. Tony was the kind of painter who was somehow
connected with the paint and he could colormatch and stand up the
metalflake replacement paint like the original, so you couldn't tell
the difference. A true _artist_.

Have you talked with painters or automotive paint supply shops there
across the pond, Chris? They're fonts of knowledge, if you can get
them to spare you a few minutes.

--
Give me the luxuries of life.
I can live without the necessities.
--anon
  #10  
Old February 15th 17, 10:18 PM posted to rec.crafts.metalworking
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Posts: 578
Default Modern car paint and rust

On 2/12/2017 4:03 PM, wrote:
On Sunday, February 12, 2017 at 3:01:15 PM UTC-5, Clare wrote:
On Sun, 12 Feb 2017 10:43:40 -0800 (PST), Christopher Tidy
wrote:

Hi folks,

Quick question. Many cars from the 1980s used to rust badly. Sometime in the 1990s, this changed - and quite suddenly. Does anyone know what specific changes were made to the paint composition and surface treatment? I can only find vague allusions in most articles.

Thanks,

Chris

Big thing was change to the surface preparation of the steel to
either electrostatic wet application or full body dip of a high
quality etching primer which I believe contains Zinc.
This was combined with the use of high strength steels and
"galvanized" steel in rust prone areas.


Right. It's better coatings, better primers and protection, and better application. Read, water-based coatings that often are based on urethanes; phosphate and weldable, etching primers; galvanizing in rust-prone areas; and electrophoresis and electrostatic application. The first water-based coatings -- used into the '80s by some manufacturers -- had poor adhesion and didn't weather well. They're MUCH better now.

All of this became more necessary as body panels got thinner, with the use of AHSS (advanced high-strength steels; a continuing evolution of the HSLA [high-strength, low-alloy] steels that were first used in the '70s). Rust is potentially a bigger problem than ever because the steel is thinner.


Why the change to base plus clear coat?
I took an auto body class in high school, we had lacquer and enamel,
44 years ago.
The hood on my sons Toyota had faded and was blotchy. So I went to
the paint store to buy paint. I thought I wanted lacquer, I was quickly
educated that I wanted a base and a clear coat. It turned out good
especially for an outdoor job. We did end up with a small hazy area,
when we started the motor to move it in the garage, before the dew came.
Just one area on the right side near the windshield. I suspect
it would buff out, but he took the car back to college, so haven't
tried. Mikek

 




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